江苏沿江棉区第三代棉铃虫防治指标研究

通过人工接虫为害，获得了棉铃虫各龄期幼虫在棉花上的为害量和为害损失。并观察了不同年份棉铃虫卵和各龄幼虫的自然存活率。在此基础上．研究得出了自然状态下第3代棉铃虫的防治指标，其值为百株累计卵量100粒，或当日百株新增卵量25粒。与用固定虫量研究方法得出的指标相比，该指标更合理、更经济可行。

Studies on the economic threshold for the third generation of cotton bollworm in cotton region of Yangtse river basin in Jiangsu Province

Damage amount and damage loss to cotton by the various instar larvae of cotton bollworm,Helicoverpa armigera were got through inoculating larvae to cotton plant.Natural survival rate of eggs and the various instar larvae in different years were also investigated. On this basis,the economic threshold of the third generation of cotton bollworm under natural condition was worked out to be 100 accumulated eggs per 100 plants,or 25 increased eggs per 100 plants in one day.This threshold was more reasonable, economical and practical than that calculated by the method with the fixed larvae number.